Diffusion Data Fields
    • 22 Sep 2022
    • 2 Minutes to read

    Diffusion Data Fields


    Article summary

    Data Input

    In order to input the required information for this pollutant into the Water Quality model, the user needs to make sure that the Tab Diffusion appears in the WQ General Tab (please follow the description on the page Preparing a Water Quality Datafile for this). Then the user needs to select the Tab Diffusion and type in the necessary information for this pollutant in the fields which are shown on this Tab. Alternatively the necessary information for this pollutant can be typed in the .con file opened in a Textpad editor in the datafile format mentioned below.

    Datafile format

    Depending on the form of dispersion coefficient which the user wishes to simulate there are five different data formats.

    For constant diffusion everywhere within the model use:

    Line 1       DIFFUSION

    Line 2       CONSTANT

    Line 3       d0

    Where:

    DIFFUSION =   keyword

    CONSTANT =   keyword

    d0=    Value of constant dispersion coefficient, D0(m2/s).

    For a variable value of the constant diffusion coefficient use:

    Line 1      DIFFUSION

    Line 2      VARIABLE

    Line 3      label, d0

    Above line is repeated for each node in the model.

    Where:

    DIFFUSION =    keyword

    VARIABLE =    keyword

    label =    Node label

    d0 =    Value of constant dispersion coefficient, D(m2/s).

    For estuary type diffusion use:

    Line 1       DIFFUSION

    Line 2       ESTUARY

    Line 3       azero, uzero, szero, dzero

    Line 4       d0, d1, d2

    Where:

    DIFFUSION =    keyword

    ESTUARY =    keyword

    label =    Node label

    d0 =    Value of constant dispersion coefficient, D(m2/s).

    azero =    Representative cross-sectional area at seaward boundary (m2)

    uzero =    peak tidal velocity at seaward boundary (m/s)

    szero =    salinity at seaward boundary (ppt)

    dzero =    representative saline intrusion length (km).

    d0, d1, d2 =    Value of empirical longitudinal dispersion coefficients D, Dand D(m2/s).

    For river applications use:

    Line 1       DIFFUSION

    Line 2       RIVER

    Line 3       d0, d1

    Where:

    DIFFUSION =    keyword

    RIVER =    keyword

    d0, d1 =    Value of longitudinal dispersion coefficients D(m2/s) and D

    Where the user wishes to use different types of dispersion coefficients in different parts of the model use:

    Line 1       DIFFUSION

    Line 2       DYNAMIC

    Line 3       azero, uzero, szero, dzero

    Line 4       Label, type, d0(n), d1(n), d2(n)

    Line 4 is repeated for each node.

    Where:

    DIFFUSION =    keyword

    DYNAMIC =    keyword

    azero =    Representative cross-sectional area at seaward boundary (m2)

    uzero =    peak tidal velocity at seaward boundary (m/s)

    szero =    salinity at seaward boundary (ppt)

    dzero =    representative saline intrusion length (km).

    Label, type, d0(n), d1(n), d2(n) = Node label, diffusion type (keyword 'RIVER' or 'ESTUARY'), value of longitudinal dispersion coefficients D, Dand D(m2/s). (If type = 'RIVER' then D2 is not used and should be set to zero by the file editor).


    Overview
    Diffusion


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